De-aeration of viscous grinding/mixing stock and, in particular of pasty or highly viscous stock, such as paints, is exceptionally difficult. A journal article by Engels entitled "Improvement of the efficiency of wet operating agitating mills through full-volume utilization and avoidance of air inclusions" published in the periodical journal "FARBE UND LACK" Vol. 10, 1969, describes the transfer of ground stock from a closed agitating mill into a collecting container. The agitating mill has a separator device consisting of a cylindrical sieve which holds back the medium present in the grinding chamber of the agitating mill. A storage container preceding the mill and a collection container behind the agitating mill are both subjected to a vacuum. The grinding chamber of the mill can also be subjected to a vacuum. This well-known configuration is inoperable, because the grinding stock tends to foam under the vacuum in the grinding chamber; the grinding medium also floats up and clogs the vacuum line. On the other hand, if vacuum is supplied only within the collection container, only a very small portion of the air is removed from the ground stock.
It is also known to add a dispersing and homogenizing aggregate to a heatable mixing tank and to provide successive vacuum de-aeration in a cone-shaped container in the form of a cone standing on its point, into whose upper end enters a pipe from the mixing tank. The viscous material supplied by this pipe line is deposited on a rapidly revolving disk, which throws off the relatively finely divided material while the container is subjected to a vacuum. A discharge pump is attached to the lower end of the container. This known embodiment works satisfactorily, but represents a considerable additional equipment expense.
It is further known to process pasty materials in a rolling mill, specifically in single or triple rolling mills in which the air is literally squeezed out of the material between the rollers.